This invention relates to pulverizers and in particular to apparatus for classifying pulverized material that permits reduction in the height of the pulverizer.
Present pulverizers have centrifugal separators in the upper region of the pulverizer within the pulverizer housing between the top of the bowl and the outlet piping. The centrifugal separator is quite large requiring approximately twice the height between the top of the bowl and the outlet piping than would be required without the centrifugal classifier. Material that has been pulverized, typically coal, is entrained in the airflow passing upwardly over the bowl and passes through a plurality of vanes in the upper portion of the centrifugal separator. The vanes impart a circumferential velocity component to the gas flow as it enters the centrifugal separator. The heavier pulverized material is separated from the gas flow by the centrifugal separator and is returned to the bowl through an inverted conical lower portion of the centrifugal separator to be pulverized again. The finer pulverized particles remain entrained in the airflow and pass through the centrifugal separator to the outlet piping. In this manner prior art pulverizers classify pulverized material in a centrifugal separator that is within the pulverizer housing with the circumferential velocity component required to accomplish centrifugal separation imparted by the vanes adjustable by varying the angle of the vanes relative to the centrifugal separator.
As pulverizers of larger capacity and hence larger physical size are developed, the overall height of the pulverizer must be limited. It is an object of this invention to provide apparatus for classifying material pulverized in a pulverizer that permits a reduction in the height of the pulverizer while maintaining the ability to control the size of the pulverized particulate matter exiting the pulverizer through the classifying apparatus.